Compatibilizer, description

SCFT today is one of the most commonly used tools in polymer science. SCFT is based on de Gennes-Edwards description of a polymer molecule as a flexible Gaussian chain combined with the Flory-Huggins "local" treatment of intermolecular interactions. Applications of SCFT include thermodynamics of block copolymers (Bates and Fredrickson, 1999 Matsen and Bates, 1996), adsorption of polymer chains on solid surfaces (Scheutjens and Fleer, 1979,1980), and calculation of interfacial tension in binary polymer blends compatibilized by block copolymers (Lyatskaya et al., 1996), among others. 

The thermodynamics of macromolecular solutions with small molecules is described in Sect. 7.1. A term frequently used to describe solutions of macromolecules is blend. The word is obviously derived from the mixing process and should only be used when the resulting system is not fully analyzed, i.e., one does not know if a dissolution occurred or the phases remained partially or fully separated. The term blend should best be used only if a phase-separated system has changed by vigorous mixing to a finer subdivision, containing micro- or nanophases. The differences between nanophase separation and solution can be rather subtle, as is seen, for example, in the thermodynamic description of block copolymers (see Sect. 7.1). Micro- and nanophase-separated systems can often be stabilized by compatibilizers that may be block copolymers of the two components. Their properties can be considerably different from macrophase separated systems or solutions and, thus, of considerable technical importance. 

Description (EMAC) Used as an impact modifier and compatibilizer good tie-layer in coextrusion, with broad temperature range translucent/clear colour ... 

Both component polymers form separate, but intermingled phases (Figure 1). Since polystyrene and polyethylene are immiscible, simple compounding gives very brittle products. Addition of a compatibilizer (e.g., RCM1 or RCM 2) makes it possible to obtain useful blends. Morphology of polystyrene/polybutadiene blends can be seen from Figures 5 and 6 in Polystyrol description. 

Although the exact explanation and theoretical description of the compatibilizers activity remains an open field of research, the morphology changes induced by effective compatibilization are qualitatively the same. The efficiency of a compati-bilizer can be determined from emulsification curves showing the size of the dispersed particles as a function of compatibUizer concentration [129,130]. 

A very interesting problem is the adsorption of block copolymers at the interface between incompatible homopolymers,which lower the interfacial tension and therefore act as compatibilizing agents in such blends. This phenomenon has been studied theoretically (e.g.. Refs 200-203, 207), experimentally (e.g.. Ref. 206), and by Monte Carlo simulation. In the last work the A, B homopolymers are not included explicitly in the simulation, however, and their existence shows up only indirectly via suitable energy parameters which differ in the A-phase (for z > T/2) from those in the B-phase (for z < Ljl). The A-B interface hence is sharp on the scale of the lattice spacing and treated as strictly localized. Wang et al treat L lattices with lattice sizes up to = 50 and up to 400 chains of composition Na= Nb = ox variable / with N = 10 up to /= 3/4, and discuss the description of the block copolymer adsorption at the A-B interface in terms of Langmuir-type isotherms. 

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